Friday, July 28, 2017

Date: July 27, 2017Source: Rice UniversitySummary: A high school student's project removes more than 99 percent of heavy metal toxins from water. A new article demonstrates its potential for water remediation in developing nations around the world.

Plain quartz fiber, top, gains the ability to remove toxic metals from water when carbon nanotubes are added, bottom. The filters absorbed more than 99 percent of metals from test samples laden with cadmium, cobalt, copper, mercury, nickel and lead. Once saturated, the filters can be washed and reused.Credit: Barron Research Group/Rice University

Carbon nanotubes immobilized in a tuft of quartz fiber have the power to remove toxic heavy metals from water, according to researchers at Rice University.

Prize-winning filters produced in the lab of Rice chemist Andrew Barron by then-high school student and lead author Perry Alagappan absorb more than 99 percent of metals from samples laden with cadmium, cobalt, copper, mercury, nickel and lead. Once saturated, the filters can be washed with a mild household chemical like vinegar and reused.

The researchers calculated one gram of the material could treat 83,000 liters of contaminated water to meet World Health Organization standards -- enough to supply the daily needs of 11,000 people.

The lab's analysis of the new filters appears this month in Nature's open-access Scientific Reports.

The robust filters consist of carbon nanotubes grown in place on quartz fibers that are then chemically epoxidized. Lab tests showed that scaled-up versions of the "supported-epoxidized carbon nanotube" (SENT) filters proved able to treat 5 liters of water in less than one minute and be renewed in 90 seconds. The material retained nearly 100 percent of its capacity to filter water for up to 70 liters per 100 grams of SENT, after which the metals contained could be extracted for reuse or turned into a solid for safe disposal.

While the quartz substrate gives the filter form and the carbon nanotube sheath makes it tough, the epoxidation via an oxidizing acid appears to be most responsible for adsorbing the metal, they determined.

Alagappan, now an undergraduate student at Stanford University, was inspired to start the project during a trip to India, where he learned about contamination of groundwater from the tons of electronic waste -- phones, computers and the like -- that improperly end up in landfills.

"Perry contacted me wanting to gain experience in laboratory research," Barron said. "Since we had an ongoing project started by Jessica Heimann, an undergraduate who was taking a semester at Jacobs University Bremen, this was a perfect match."

Barron said the raw materials for the filter are inexpensive and pointed out the conversion of acetic acid to vinegar is ubiquitous around the globe, which should simplify the process of recycling the filters for reuse even in remote locations. "Every culture on the planet knows how to make vinegar," he said.

"This would make the biggest social impact on village-scale units that could treat water in remote, developing regions," Barron said. "However, there is also the potential to scale up metal extraction, in particular from mine wastewater."

Alagappan's research won a series of awards while he was still a high school student in Clear Lake, a Houston suburb, as well as a visiting student in Barron's Rice lab. First was the top prize for environmental sciences at the Science and Engineering Fair of Houston in 2014. That qualified him to enter the Intel International Science and Engineering Fair in Los Angeles the next year, where he also took the top environmental award.

He booted that into the top prize at the 2015 Stockholm Junior Water Prize, where the crown princess of Sweden presented him with the honor.

"It's been a tremendous honor to be recognized on an international level for this research, and I am grateful for the opportunity to work on this project alongside such a talented group of individuals," Alagappan said. "I also especially appreciated being able to meet with other young researchers at the Intel International Science Fair and the Stockholm Junior Water Prize, who inspired me with their firm commitment to elevate society through science and technology."

Thursday, July 13, 2017

Date: July 12, 2017Source:American Chemical SocietySummary: Hydraulic fracturing has enabled a domestic oil and gas boom in the US, but its rapid growth has raised questions about what to do with the billions of gallons of wastewater that result. Researchers now report that treating the wastewater and releasing it into surface waters has led to the contamination of a Pennsylvania watershed with radioactive material and endocrine-disrupting chemicals.

Hydraulic fracturing has enabled a domestic oil and gas boom in the U.S., but its rapid growth has raised questions about what to do with the billions of gallons of wastewater that result. Researchers now report that treating the wastewater and releasing it into surface waters has led to the contamination of a Pennsylvania watershed with radioactive material and endocrine-disrupting chemicals. The study appears in ACS' journal Environmental Science & Technology.

In 2015, the unconventional oil and gas extraction method known as hydraulic fracturing, or "fracking," accounted for more than one-half of oil production and two-thirds of gas production in America, according to the U.S. Energy Information Administration. The method's market share is likely to increase even further. Although the technique has resulted in a shift away from coal, which could reduce greenhouse gas emissions, it produces large amounts of wastewater containing radioactive material, salts, metals, endocrine-disrupting chemicals and polycyclic aromatic hydrocarbons that could pose risks to the environment and human health. A Pennsylvania report estimates that in 2015, 10,000 unconventional oil and gas wells in the Marcellus Shale produced 1.7 billion gallons of wastewater. The facilities that collect the water provide only limited treatment before releasing it into surface waters. Bill Burgos and colleagues at Penn State, Colorado State and Dartmouth wanted to see what impact this strategy of treating and releasing fracking wastewater might be having.

The researchers sampled sediments and porewaters from a lake downstream from two facilities that treat fracking wastewater in Pennsylvania. Their analysis detected that peak concentrations of radium, alkaline earth metals, salts and organic chemicals all occurred in the same sediment layer. The two major classes of organic contaminants included nonylphenol ethoxylates, which are endocrine-disrupting chemicals, and polycyclic aromatic hydrocarbons, which are carcinogens. The highest concentrations coincided with sediment layers deposited five to 10 years ago during a peak period of fracking wastewater disposal. Elevated levels of radium were also found as far as 12 miles downstream of the treatment plants. The researchers say that the potential risks associated with this contamination are unknown, but they suggest tighter regulations of wastewater disposal could help protect the environment and human health.

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The American Academy of Environmental Engineering and Scientists is a not-for-profit 501(c)(6) organization serving the Environmental Engineering and Environmental Science professions by providing Board Certification to those who qualify through experience and testing. The Academy also provides training through workshops and seminars, participates in accrediting universities, publishes a periodical and other reference material, interacts with students and young professionals, sponsors a university lecture series, and rewards outstanding achievements through its international awards program.